The overall objectives are to determine how information carried on the pulmonary PCO2(t) and PO2(t) signals effect ventilation, rate and depth. Also to perfect techniques for studying biological control systems with subtle, meaningful manipulations of feedback signals. The rationale behind this research is to try to understand the causal relationship between alveolar PCO2(t) changes and ventilation on a purely informational basis. The constraints determining the parameters of this relationship may be described on an information basis without initially considering the exact anatomical locations or biochemical mode of transmission of any of the components. First we must know what happens before we can say where and how it happens. BIBLIOGRAPHIC REFERENCES: Berger, P.J., R.D. Tallman, Jr., and A.L. Kunz. EFfect of Temporal Changes in Inspiratory FCO2 on Intrapulmonary CO2 Receptor Discharge in Decerebrate Ducks. Fed. Proc. April 1977, in press. Tallman, R.D., Jr., and A.L. Kunz. Changes in Inspiratory Duration as a Function of when FCO2 is Increased in the Inspiratory Gas Flow of Birds. Proceeding XXVIIth International Congress of Physiological Sciences, Paris, 1977, in press.